They will naturally be downplayers on every side. But the frequency of downplaying is not equal. Nintendo evokes a particular hatred as many still see it as a threat to what they perceive to be the natural order of things.
Nah, both Nintendo, PlayStation, Xbox, and PC have those extreme "fans" that are only capable of seeing things from their own biased perspective.
Many PS related threads on this site are derailed as well.
I haven't disagreed with any of that. But beyond just brand loyalty, there's a different kind of negative reaction Nintendo provokes among many, the reaction caused when the perceived norm, the "way things are/should be" is disrupted.
The PS1, PS2, and PS4's dominance for many years created a paradigm where, in the home space at least, complete Sony domination was seen as the natural order of things. First the Wii and now the Switch challenged this paradigm. This kind of disruption almost always provokes strong negative reactions.
Add to that the persisting associations many still hold that Nintendo = kiddy/casual = bad, and PS = hardcore = good, and Nintendo success elicits a particular anger distinct from just the usual "my plastic box is better than yours."